Japanese researchers at RIKEN Advanced Science Institute in Wako and University of Tokyo discovered a method of making a novel material that bends in response to light. The press release claims that the new material could be used in artificial muscles, though why light would be a better way to control muscles is not clear.
They made their discovery while studying a polymer in which each side chain, or bristle, of the brush structure incorporates light-responsive azobenzenes—two benzene rings separated by a pair of nitrogen atoms. When hit by UV light, the bond between the nitrogens rearranges, contracting the side chain.
The researchers used this photoisomerization behavior to confirm the remarkable long-range order of the polymer structure. Because the side chains were all aligned, when those at the surface were hit by light they curled up in concert, bending the film. A second beam of light at a different wavelength reversed the isomerization process, and the film relaxed back to its original shape.